title: Ontogenetic expression of maternal and zygotic genes in Atlantic cod embryos under ambient and thermally stressed conditions.
abstract: The embryonic stages of Atlantic cod (Gadus morhua) are especially sensitive to incubation temperature. The purpose of the present study was to follow the ontogenetic expression of selected genes of maternal (pou2 and nanog) and zygotic origin (hsp70, hsp90α and stip1), in Atlantic cod embryos under ambient and thermally stressed conditions. The study also investigated how reference genes can be applied to studies on embryonic development, when maternal genes are degraded and the zygotic transcription stabilizes. Three batches of eggs were reared and gene expression profiles from the reference and target genes were determined. The embryos were reared at ambient 6 °C, and 10 °C for continuous long-term and acute short-term heat exposure. Both pou2 and nanog showed reduced expression whereas the zygotic and reference genes showed increased expression until stabilizing at gastrulation, when a normalized ontogenetic expression profile of target genes could be generated. pou2 and nanog were not affected by thermal stress. In contrast, hsp70 and hsp90α were upregulated after short-term heat exposure at the early blastula (hsp70 only), late blastula, 50% epiboly and 90% epiboly stages (hsp90α only). Long-term heat exposure of Atlantic cod embryos upregulated both hsp70 (90% epiboly) and hsp90α (90% epiboly and 20-somites). The results suggest that a cellular defense mechanism is activated even in the earliest stages of embryonic development, a period critical to developmental temperature.
authors.affiliation: National Institute of Nutrition and Seafood Research (NIFES), PO Box 2029 Nordnes, 5817 Bergen, Norway. ksk@nifes.no
authors.forename: Kaja H
authors.initials: KH
authors.lastname: Skjærven
authors.forename: Pål A
authors.initials: PA
authors.lastname: Olsvik
authors.forename: Roderick Nigel
authors.initials: RN
authors.lastname: Finn
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Holen
authors.forename: Kristin
authors.initials: K
authors.lastname: Hamre
mesh_terms: D000818:Animals; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D048389:Gadus morhua / Q000196:embryology* / Q000235:genetics; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006979:Hyperthermia, Induced; D008297:Male; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics*; D015053:Zygote / Q000502:physiology*
chemical_list: D029941:Fish Proteins; D006360:Heat-Shock Proteins; D018398:Homeodomain Proteins; D050814:Octamer Transcription Factor-3